Finite element analysis of model piles axially loaded in sands

Open Journal of Civil Engineering, 2020

This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a structure represents the essential structural part of it, because it ensures its bearing capacity. Among the types of foundation, deep foundation is the one for which from a mechanical point of view, the justification takes into account the isolated or combined effects of base resistance offered by the soil bed and lateral friction at the soil-pile interface; the latter being the consequence of a large contact surface with the surrounding soil; hence the need to study the interaction between the soil and the pile in service, in order to highlight the characteristics of soil which influence the mechanical behavior of pile and therefore the stability of the structure. In this study, the reinforced concrete pile is supposed to be elastic, and characterized by a young's modulus (E) and a Poisson's ratio (ν). The soil obeys to a Camclay model characterized by a cohesion (c), an initial voids ratio (e 0 ), shearing resistance angle (φ) and a pre-consolidation pressure (P 0 ). A joint model with a Mohr Coulomb behavior characterizes the soil-pile interface. The loading is carrying out by imposing a vertical monotonic displacement at the head of pile. The results in terms of stress and displacement show that the bearing capacity of the pile is influenced by various soils characteristics, it appears that the vertical stress and the force mobilized at rupture increase when the initial pre_consolidation pressure, the cohesion and the internal friction angle of soil increase; and when the initial soil voids index decreases.

International Journal of Advanced Structural Engineering, 2014

This paper presents a numerical study of pilesoil interaction due to application of axial and lateral loads to piles in sand. The pile-soil interaction was analyzed using the finite difference (FD) software LPILE and two finite element (FE) software. The three-dimensional (3D) FE models of pile-soil interaction have been created using Abaqus/Cae and SAP2000. Various types of soft soil were studied, such as loose, medium, and dense sand. A lateral displacement of 2 cm was applied to the top of the pile while maintaining a zero slope in a guided fixation. A combined lateral and axial load of 300 kN was also studied. The paper compared between the bending moments and lateral displacements along the depth of the pile obtained from the FD solutions and FE analyses. A parametric study was conducted to study the effect of crucial design parameters such as the modulus of elasticity of soil and the number of nonlinear soil springs that can be used to model the soil. A good agreement between the results obtained by the FE models and the FD solution was observed. Also, the FE models were capable of predicting the pile-soil interaction for all types of soft soil.

Engineering Structures, 2003

In this paper, inelastic pile soil structure interaction is analyzed by using a hybrid type of numerical method. Piles and structural elements are modeled as linear finite elements and soil half space is modeled by using boundary elements. Inelastic modeling of soil media is presented by introducing a rational approximation to continuum with nonlinear interface springs along the piles. For this purpose, modified Ö zdemir's nonlinear model is implemented and systems of equations are coupled for piles and pile groups at interacting nodes. To verify the proposed algorithm, four experimental results from previously conducted tests under static loads are compared with those obtained from present analysis.

2012

This paper presents a methodology to understand the interface behavior of soil and pile under transient loading. Previous works by Trochanis (1991), Bently and Naggar (2000) and others gave an insight to the problem. But this paper illustrates the research methodology developed to understand the dynamic behavior of pile and soil by taking the soil yielding effects and also the interface effects. A detailed parametric study has been done to understand the behavior of the same by varying the length of the pile for various soil conditions. For the purpose of comparison, soil model size was taken as 15m x 10m x 11m with pile cross section as 0.5 X 0.5 m and length of pile as 10m. For this we have developed a program for modeling the soil pile structure interaction using three dimensional Finite Element Method in MATLAB R2009a, the details of the same have been given in this paper along with the validity of it with benchmark problems in the literature.

WIT Transactions on State of the Art in Science and Engineering, 2014

The behaviour of deep foundation under static loads has been widely investigated and the available calculation procedures can be considered suitable for the current engineering applications. However, pile behaviour under seismic loading is more complex and less known, because it involves the simultaneous action of inertial forces arising from the superstructure (inertial interaction) and of the soil deformations arising from the seismic waves (kinematic interaction). Italian code DM 14/01/2008 requires the dynamic soil-structure interaction in seismic foundation design to be taken into account, but it does not give any information about criteria for the evaluation of kinematic interaction strains. Experimental evidence and theoretical considerations by many authors show that the kinematic interaction alone may induce high stresses in piles, especially near an interface between a soft and a rigid soil layer. In this work pile behaviour due to kinematic interaction with soil will be examined. An approach based on a differential equation proposed in the relevant technical literature will be used. The analysis is focused on the response of a single pile in a heterogeneous three-layer soil profile.

This paper focuses on the application of sub grade reaction method for the analysis of laterally loaded piles embedded in cohesion less soils. The sub grade reaction method considers the pile as a flexible beam on the elastic foundation and replaces soil as a series of elastic, closely spaced but independent springs. This method has the advantage of being relatively simple, and single layer foundation in cohesion less soil is considered in the present study. The pile deflection, Slope, bending moment and shear force is calculated using this method and the same has been validated with finite element based ANSYS software. The code IS 1911 has been used for values of Constant subgrade reaction.

Soils and Foundations, 2019

This paper presents a new method for analyzing the nonlinear response of a single, vertical pile with the circular cross-section under torque in layered soils. The nonlinear stress-strain relationships of both soil-pile interface and soil are approximated by the hyperbolic model, whereas the pile material is elastic. The torsional spring stiffness of the soil-pile interface and the soil are determined by traditionally available methods. A four-node finite element model for the soil-pile interface is proposed to represent nonlinear behaviors of the soil-pile interface and the soil, separately. A new iterative scheme for nonlinear analysis of a single pile under torque is also developed that avoids having to solve a large number of simultaneous equations found in traditional solution schemes. The new solution method is based on the tangential stiffness of the soil-pile interface and soil springs, which are determined at each load step. From this solution scheme, an equivalent stiffness of the soil-pile-interface system of each pile element is calculated from the bottom element to the top element while torque and angle of twist are calculated from the top to the bottom elements. The solution gives the distribution of the angle of twist and torque along the pile, and the equivalent stiffness of the soil-pile system and torque-angle of twist curves at any depth. The solution method can be easily applied to the practice field in nonlinear analysis and in designing a single pile under torque in layered soils. The analysis results using the new solution scheme compared well with the results from other analytical methods studied by previous researchers. The proposed method is also used to predict the behavior of two full-scale piles under torques. The predictions are in good to excellent agreement with measurements.

Short stubby piles like monopiles and large diameter drilled shafts undergo rigid body translation and rotation when subjected to a lateral force and/or a moment at the head. A method of analysis for these piles embedded in multi-layered elastic soil is developed using the variational principles of mechanics. Using this analysis, the soil resistance against pile movement can be rigorously related to the soil elastic constants, and the pile head displacement and rotation can be quickly calculated. The equilibrium equations for pile and soil displacements are obtained using the principle of virtual work and solved using an iterative algorithm. Pile responses obtained from the analysis match well with those obtained from three-dimensional finite element analyses in which the same inputs of loads, geometry, and material properties are given. Based on the new analysis, fitted equations for soil resistance parameters are developed, which can be used to directly calculate the pile head displacement and rotation without the use of the iterative algorithm. Numerical examples are provided that demonstrate how the method can be used to analyse practical problems. ARTICLE HISTORY

In this paper, pile and soil are simulated by Solid-3D element. In the computational model, contact surfaces between pile and soil are imitated by contact element in ANSYS software. Analysis results of this three-dimensional model were compared with another mathematics model of previous authors, such as: Brinch Hansen, Broms, Reese and Matlock, Poulos, K.X Zavriev.

Earthquake Resistant Engineering Structures VII, 2009

The behaviour of deep foundation under static loads has been widely investigated and the available calculation procedures can be considered suitable for the current engineering applications. However, pile behaviour under seismic loading is more complex and less known, because one can find the contemporary action of inertial forces rising from the over-structure (inertial interaction) and of the soil deformations rising from the seismic waves (kinematic interaction). Italian code DM 14/01/2008 requires the dynamic soil-structure interaction in seismic foundation design to be taken into account, but it does not give any information about kinematic interaction strains evaluation criteria. Experimental evidences and theoretical considerations of many authors show that simply the kinematic interaction may induce high stresses on piles, especially near an alternation between a soft and a rigid soil layer interface. In this work pile behaviour due to kinematic interaction will be examined. An approach based on the differential equation proposed by Kavvadas and Gazetas (Kinematic seismic response and bending of free-head piles in layered soil. Géotechnique, 43, N.2, 207-222, 1993) will be used. The analysis is focused on the response of a single pile in a heterogeneous three-layer soil profile.